Since we are no longer resetting rings when a Babble or Stall condition

Since we are no longer resetting rings when a Babble or Stall condition
is detected, simply keep track of the faulty xfer instead of completing
all the pending ones.

Fix a race condition where we could end up aborting a freshly enqueued
xfer when two different threads are submitting control transfers (i.e.
usbdevs(8) and a kernel driver).